The overall objective is to define the molecular mechanism(s) that regulate glycine synthesis and the flow of one carbon units in Salmonella typhimurium and Escherichia coli. Regulatory mutants will be isolated that are resistant to specific amino acid analogs. In addition, the lac structural genes have been fused to the promoter controlling glyA gene expression as a means of isolating and studying mutants with altered control of the glycine pathway. Genetic techniques (conjugation, transduction) will be used to locate the sites of these mutations on the E. coli and S. typhimurium linkage map. Physiological studies will be perforned to determine the consequences of these mutations on regulation and to determine the different regulatory components involved in the control mechanism(s). Finally the glyA gene and its controlling segment from S. typhimurium and E. coli will be cloned into plasmid vehicles and restriction mapping and DNA sequencing techniques will be used to determine the location and nucleotide sequence of the controlling segment for the glyA gene. The responses of the control segment in vitro to the addition of the components found to be important for regulation during the physiological experiments will be examined.